This invention relates to a process for the recovery of indene in high purity from mixtures of indene and organic impurities.
The art contains many examples of processes for the separation of an organic compound, such as indene, from mixtures with other organic compounds. Because of the presence of other species with close boiling points in indene rich naphtha cracker streams, the highest purity economically attainable by fractional distillation is only about 85 to 92 percent by weight. A process is disclosed in U.S. Pat. No. 1,943,078 to Kahl for the recovery of indene from fractional distillation to obtain a mixture of at least about 80 percent indene. The temperature of this mixture is then lowered to about -25.degree. C to crystallize the indene present. Centrifugation produced a compound having the freezing point of indene (-2.degree. C) in about 47 percent yield. Typically indene purities as high as about 98 weight percent can be obtained by the skillful crystallization and centrifugation of mixtures of this type. Centrifugation is, however, a high energy, high maintenance unit operation and it would be desirable to provide a method which avoids these costs.
Schmid et al., USP AT. No. 3,804,915, teach a process for recovering p-xylene at purities greater than 99.5 weight percent from mixtures of o--, m--and p-xylene. The process comprises crystallizing p-xylene from the xylene mixture at a low temperature, removing the crystals from the mother liquor, and subsequently passing an inert medium through the crystals to remove any adhering mother liquor. However, all the components of the mother liquor have melt points below that of p-xylene.